Passing GD_NULL or GD_UNKNOWN to this macro will return zero. For the other types, the value returned is simply the bit-size encoded in the type symbol divided by eight, so, e.g., GD_SIZE(GD_COMPLEX64) will return 8.

No error checking is performed on type: behaviour resulting from passing something other than the symbols listed above to this macro is unspecified. See gd_getdata(3) for the meaning of the above symbols.